1. Field of the Invention
Embodiments of the invention generally relate to semiconductor and electronic manufacturing processes, more particularly, to a process for forming a metal contact on a silicide junction on a substrate.
2. Description of the Related Art
Metal contacts are frequently formed on semiconductor devices to integrate them into electrical circuits. In a typical semiconductor device, such as a Metal Oxide Silicon Field Effect Transistor (MOSFET), metal contacts may be formed on the gate structure, and on the source and drain junctions. These contacts must be electrically coupled to the metal oxide layer of the gate structure, and to the amorphous silicon region of the source and drain junctions, for the device to function.
Aluminum metal has been used for the contacts due to its low electrical resistivity. As device geometry shrinks, however, the tendency of silicon and aluminum to diffuse through each other degrades electrical properties of the smaller devices. Tungsten is frequently used for contacts in small devices because it is resistant to diffusion with silicon. Resistivity of tungsten is nearly twice that of aluminum, however, and the smaller devices of the future will require lower resistivity materials. Barrier films such as silicon carbides, silicon nitrides, metal nitrides, and silicon oxynitrides, may be used to reduce diffusion at layer interfaces, but they also increase resistivity at those interfaces. Use of barrier layers also reduces the size of contact holes, resulting in smaller contact size and further increased resistivity.
Thus, there is a need for a method of integrating a conductive contact with a cobalt silicide region of a semiconductor device with low resistivity and low diffusion of impurities into the metal contact.